It’s such a simple word: just four letters. And, yet, defining it is not so simple. What, exactly, is ragu? Is it a tomato sauce? A meat sauce? A brand name?

The quickest answer is yes. But the true answer, like the sauce itself, is more complex. True ragu is not something you pour out of a jar. It cannot be thrown together with ground beef and tomatoes on a Tuesday night. Making ragu is an artful, deliberate exercise that takes hours. It is among the most iconic Italian dishes, and it is not an exaggeration to say that throughout Italy it is the measure of a good home cook.

“In some ways, it represents the essence of the way we cook; simple to make, but only if the ingredients have been carefully selected, and as long as you take the required amount of time to make it,” says Angela Frenda, food editor at the Milan-based newspaper Corriere della Sera. “No shortcuts are accepted, Instant Pot or otherwise.” (More on that later, IP lovers.)

At its most basic, ragu can be defined as a range of slow-cooked meat sauces typically paired with pasta. The most famous iterations are Bolognese ragu, the rich ground-meat sauce enhanced with milk and cream from the Emilia-Romagna region; and Neapolitan ragu, made by braising large pieces of pork, beef or a mix in tomato puree. Really, the two could not be more different.

Neapolitan ragu is a robust tomato sauce infused with the flavor and fat of braised meat, and usually served with short, sturdy pasta. Bolognese-style ragu is dense, almost spoonable, delicately flavored and with a minimal amount of tomato. It is typically served in lasagne or with fresh egg tagliatelle. But never spaghetti. Why? Because, for the most part, people in Bologna eat tagliatelle. Indeed, the mayor of Bologna, Virginio Merola, recently launched a social media campaign to inform people that the dish known in many parts of the world as “spaghetti Bolognese” does not exist. He calls it “fake news.”

There is also a long-standing dispute between the Bolognesi and the Neapolitans over whose ragu came first, but that is unlikely to be resolved anytime soon. Besides, there are now variations across Italy. In Tuscany, which borders Emilia-Romagna, ground pork and/or beef are the meats of choice, but dairy is omitted. Farther north, ground rabbit or duck becomes the main ingredient. Ragu from Abruzzo leans more toward the Neapolitan style. Lamb is often part of the mix, not surprising in this mountainous region where sheep farming is still a way of life.

These regional sauces have one essential element in common: an invisible ingredient called time. A great ragu needs time to transform from a pot of disparate ingredients into something whole, rich, complex and deeply satisfying.

“A gentle, long, slow simmering — so it barely blips on the stove — has always been regarded as an essential ‘ingredient’ of a good ragu,” says Jenny Linford, author of “The Missing Ingredient: The Curious Role of Time in Food and Flavor.” Cook a ragu quickly, she warns, and the results are very different: “The elements remain separate, rather than melding together, with the result being simply meat in a comparatively insipid, watery tomato sauce — two-dimensional in flavor, a world away from the classic rich ragu so beloved of Italians.”

The word “ragu” can be traced back to French ragout, a slow-cooked stew made with meat or fish and vegetables, or vegetables alone. It is believed to have made its way to Italy sometime after Napoleon’s invasion and occupation in the late 18th century. It wasn’t until decades later that slow-cooked meat and pasta came together. There is a recipe for maccheroni alla Bolognese in Pellegrino Artusi’s 1891 cookbook “La Scienza in Cucina e l’Arte di Mangiar Bene” (Science in the Kitchen and the Art of Eating Well). The sauce he describes is, essentially, a prototype for traditional Bolognese ragu, featuring slowly sauteed vegetables and veal, plus broth and nutmeg, but no tomato. Tomatoes came later, but only sparingly, as a way of deepening the flavor.

In Naples and the south, where Italy’s best tomatoes come from, they feature prominently in ragu. Neapolitan ragu is considered a “piatto unico,” something beyond merely a dressing for pasta, says Frenda, who is from Naples. “My two grandmothers, Angela and Olga, considered ragu the prize at the end of the week. It was served on Sunday, because then we had time to sit at the table and enjoy the meal: first the pasta with sauce; and then, in the same dish, the meat that was cooked in the sauce. And, of course, bread to wipe the plate clean.”

Ragu was a Sunday special in our home when I was growing up, as well. My mother was from Abruzzo, but she became known in our New Jersey community for her Bolognese sauce. I remember being fascinated by the day-long process; the quiet sizzling of the vegetables; the heady, almost sweet aroma of the browning meat as it gradually turned a caramel color; the time it took for the milk to be fully absorbed into the sauce; and then the final slow simmer. Mom’s recipe was traditional except for one brilliant deviation: When the sauce was nearly done, she would stir in a handful of very thinly sliced strips of silky, delicately spiced mortadella. The sauce perfumed the house for days.

Making ragu remains one of my favorite weekend pastimes, especially on a blustery day in late winter, when nothing is more comforting than watching (and smelling and tasting) the transformation. Over the years I’ve developed a repertoire of at least six different ragus, including a vegetarian version. Strict definitions aside, yes, you can make a great vegetarian ragu. Apply those same principles of gentle sauteing and long, slow simmering to vegetables, and the result is as satisfying as a meat ragu.

Finally, the Instant Pot question. Given that time plays such an important role, how can an appliance whose purpose is the exact opposite — to slash cooking time — produce an acceptable rendition? I tried it a few times, with varying degrees of success. A short rib ragu was disappointing — soupy and two-dimensional in flavor, with pieces of beef and tomato that never fused into a sauce.

But I was pleasantly surprised by a Bolognese sauce I made from “Instant Pot Italian,” by Ivy Manning. The recipe had many of the same ingredients as my Bolognese but with more tomatoes — a certain amount of liquid is necessary to create steam pressure — and a pinch of baking soda to help soften the vegetables. It took just 1 hour and 15 minutes, and though it lacked the complexity of a true Bolognese (my daughter commented that it tasted more like tomato sauce with meat added to it), my family thought it tasted good tossed with pasta.

So by all means, use your multicooker to make ragu. But don’t deprive yourself of learning how to do it the traditional way. Participating in the creation of this iconic dish and watching the process unfold, says Frenda, is not only satisfying, it will make you a better cook. “Ragu, like good bread, is a labor of love and of life. Time is its best friend.”

Here are eight tips for successful ragu:

1. Use a heavy-bottomed pot, such as enameled cast-iron, so the ragu can cook for hours without scorching.

2. Choose the best ingredients you can afford. Ragu generally calls for cheaper cuts of meat, but be sure the quality is superior; well-marbled heritage pork will yield a more flavorful ragu than leaner mass-produced pork, whose texture leans toward sawdust with long cooking. Look for unseasoned tomato puree and paste that tastes bright rather than aggressive.

3. Most ragus start with sauteing aromatic vegetables — a soffrito. Chop these finely and uniformly, preferably by hand (a food processor tends to shred vegetables, which can prevent them from cooking evenly).

4. Brown ground meat for Bolognese sauce slowly, over medium-low heat. The aim is to gradually bring out the rich caramel flavor without making the meat tough or dry. For southern Italian-style ragu, season the meat before browning over medium-high heat to create a good sear. This will help to flavor the ragu.

5. Deglaze the pan with a good-quality, inexpensive wine and allow it to bubble off, leaving a pleasant acidity.

6. For ragus that call for broth, especially beef, use homemade. Most commercial beef broth is harsh and tastes more of onions. Homemade broth contributes to the rich umami flavor and gives the sauce a silkiness that helps it to cling to pasta.

7. Take note of how your ragu changes as it cooks. The vegetables will soften and sweeten and eventually become one with the sauce. Tomatoes will mellow, and their color will deepen to terra-cotta. The meat will give up its fat to further enrich the sauce and improve its texture.

8. Even when your ragu is done, it’s not yet finished. Let it cool to room temperature, then refrigerate it overnight. This final act truly unifies the sauce. Reheat it gently on the stove top, stirring in a little water if necessary to loosen it.

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